Income Taxes - Schedule of Reconciliation Difference of Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2011
Income Tax Disclosure [Abstract]
Amount at statutory U.S. federal income tax rate	$ 7,126		$ 5,707	$ 5,785
Change because of the following items:
State income taxes, net of federal benefit	278		236	412
Stock-based compensation	25		36	(7)
Valuation allowance change	(699)		303	21
Tax reserve release	(128)		(77)	(314)
Federal manufacturing deduction	(266)		(220)	(143)
Federal research and development credit	(324)	(200)		(53)
Other	(231)		192	(97)
Income tax provision	$ 5,781		$ 6,177	$ 5,604

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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Amount of the difference between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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